It has long been known to skilled persons in the food industry that the taste and aroma of food products are greatly affected by volatile components present in such products. For example, such components as coffee aroma, esters, acetaldehyde, various essential oils, sulfur compounds and flavorings such as vanilla, augment and enhance the perceived taste and smell of a variety of food products. Consequently, to ensure the production of food products which are of consistent quality and are attractive to consumers, it is necessary to ensure that each batch of product contains a proper, predetermined amount of such volatile components.
However, because of the volatility of these components, it is not easy to ensure that the predetermined amount of each volatile component is present in the final product as it reaches the consumer. Losses of volatile components may occur during storage prior to incorporation of the component into the food product, during the mixing of the component with the other ingredients of the food product, during baking or other cooking of the food product, during the transportation and storage involved in bringing the product to the ultimate consumer, and in some cases during the final preparation of the food product by the consumer, for example by reheating or microwaving of the food product. The extent of many of these losses are difficult to control; for example, there may be a considerable time period between the beginning and the end of the use of a batch of volatile component in a plant, so some of the batch may be in storage for far longer than another part of the same batch, while the period which elapses between the time a product leaves the plant and the time it reaches a consumer is out of the manufacturer's control.
These variations in losses of volatile components from food products may produce undesirable variations in the taste and aroma of the products as perceived by the consumer. In addition, such losses of volatile components increase the cost of the food product, since it is necessary to increase the amount of the volatile component included in the food product to compensate for the losses which occur, and many volatile components (for example, vanilla and some essential oils) are expensive.
The problems associated with volatile components are also experienced with labile components used in foods; the term "labile" is used herein to denote a material which, because of its interaction with materials present in the environment, gradually undergoes degeneration and destruction during storage. An example of a labile component is acetaldehyde, which is slowly destroyed by atmospheric oxygen.
To reduce or eliminate the aforementioned problems associated with volatile and/or labile components, attempts have been made to encapsulate such components in a matrix which reduces the volatility and/or lability of the component. Frequently, the matrix used is composed of one or more carbohydrates.
U.S. Pat. No. 2,809,895, to Swisher describes a process for encapsulation of an essential oil, such as lemon, lime or grapefruit oils, in a matrix comprising corn syrups, antioxidant and a dispersing agent. The essential oil, antioxidant and dispersing agent are added to the corn syrup, the resultant mixture is heated to 85.degree.-125.degree. C. and agitated or extruded to form an emulsion in pellet form, and the resultant particles are washed with an essential oil solvent and dried under vacuum to remove the solvent.
U.S. Pat. Nos. 2,856,291 and 2,857,281, both to Schultz, describe a process for the encapsulation of flavorants (for example, citrus oils) in a sugar base comprising sucrose, corn syrup and water. A hot emulsion of the flavorant is formed in the sugar base, and this emulsion is extruded as a stream or as globules, cooled to a plastic condition and cut into rods.
U.S. Pat. No. 2,919,989, also to Schultz, describes a modification of the process of the aforementioned U.S. Pat. No. 2,856,291 in which the sugar base used comprises, by weight, 15-40% sucrose, 10-15% lactose, 5-14% maltose, 10-50% dextrose and not more than 15% dextrin.
U.S. Pat. No. 3,041,180 to Swisher describes an essential oil flavoring composition produced by mixing glycerol and 42 DE corn syrup solids into an aqueous, semiplastic mass, which is then combined with the essential oil by means of an emulsifier. The resulting mixture is extruded into a cold solvent to form an extruded solid in which the essential oil is encapsulated by the glycerol and corn syrup solids. This extruded solid is then dried and an anti-caking agent added to produce an extruded particulate solid having an extended shelf life.
U.S. Pat. No. 3,314,803 to Dame et al. describes a method for fixing a volatile flavor such as acetaldehyde in a mannitol substrate. The acetaldehyde is fixed in mannitol by first forming a solution of mannitol and water, preferably a supersaturated solution of mannitol of between 25-45% by weight. The supersaturated solution is formed by heating with agitation 2 to 10 parts by weight of mannitol with 10 parts by weight of water at 180.degree.-212.degree. F. until all of the mannitol is dissolved in the water and no mannitol crystals remain in the solution. The solution is then cooled while acetaldehyde is added thereto. A controlled reflux admixes the volatile and the solution is then spray-dried.
U.S. Pat. No. 3,554,768 to Feldman describes a method for fixing acetaldehyde in selected carbohydrates; in this method, the acetaldehyde and the carbohydrate are uniformly mixed in water and the resultant mixture is dried to form a flavor-enhancing composition.
U.S. Pat. No. 3,704,137 to Beck describes an essential oil composition formed by mixing oil with an antioxidant, separately mixing water, sucrose and hydrolyzed cereal solids (dextrose equivalent (DE) substantially below 20, and preferably between 10 and 15), emulsifying the two mixtures together, extruding the resultant mixture in the form of rods into a solvent, removing excess solvent and finally adding an anti-caking agent, preferably silica.
U.S. Pat. No. 3,971,852 to Brenner describes a process for encapsulating an oil in a matrix comprising a polysaccharide (which may be dextrinized starch or hydrolyzed starch having a DE of 10-25) and a polyhydroxy material, which can be glucose, maltose or fructose. The ingredients are emulsified and spray dried.
U.S. Pat. No. 4,532,145 to Saleeb describes a process for fixing volatile components in an amorphous substrate to produce a moisture-stable product. In this process, a low (90-500) molecular weight water-soluble material, such as a monosaccharide or disaccharide, having a melting point of from 80.degree. to 180.degree. C., is mixed with a high (1000-6000) molecular weight water-soluble polymeric material, such as a polysaccharide, in an aqueous solution. A volatile flavorant, such as acetaldehyde, is added to this solution, and the resultant mixture is spray-dried at a temperature of from 100.degree. to 180.degree. C. at the inlet and from 50.degree. to 80.degree. C. at the outlet.
U.S. Pat. No. 4,820,534 to Saleeb et al. describes a method for fixing volatile flavorants in an extruded glass substrate which uses a matrix generally similar to that of U.S. Pat. No. 4,532,145 described above, but in which the mixture of flavorant and carbohydrates is heated above the glass transition temperature of the substrate and at or just above the melting point of the minor ingredient (the monosaccharide or disaccharide) so that the minor ingredient melts and the major ingredient (the polysaccharide) dissolves in the minor ingredient to form a molten mass, and this molten mass is extruded to produce an amorphous, homogeneous, single-phase glass containing entrapped volatile flavorant, this glass having a glass transition temperature above ambient temperature.
U.S. Pat. Nos. 4,610,890 and 4,707,367, both to Miller, describe a process for preparing a solid essential oil composition having a high content of the essential oil. This composition is prepared by forming an aqueous solution containing a sugar, a starch hydrolyzate and an emulsifier. The essential oil is blended with this aqueous solution in a closed vessel under controlled pressure conditions to form a homogeneous melt, which is then extruded into a relatively cold solvent, dried and combined with an anti-caking agent.
U.S. Pat. No. 4,689,235 to Barnes describes a process which involves generally the same steps as in the aforementioned U.S. Pat. No. 4,610,890 but in which the solution used for encapsulation comprises a mixture of a maltodextrin and hydrogen octenyl butanedioate.
One of the problems in such prior art methods for the encapsulation of volatile and/or labile components in carbohydrate matrices is the difficulty of securing a sufficiently high glass transition temperature for the glassy matrices. Although the glassy carbohydrate matrices do not have a sharp melting point characteristic of crystalline solids, they do have a glass transition temperature (also known as softening temperature), which is the temperature at which the amorphous solid matrix softens and becomes a viscous liquid.
When a glassy matrix containing an encapsulated volatile component is heated above its glass transition temperature, the encapsulated material is released by diffusion at a rate which increases with increase of temperature above the glass transition temperature. Even below the glass transition temperature, the stability of the matrix increases (and thus the loss of volatile component decreases) with the difference between the temperature of the matrix and its glass transition temperature. Thus, it is desirable to use a matrix material having a glass transition temperature well above the temperature at which the encapsulated material will be stored and used.
Another problem in such prior art methods for the encapsulation of volatile and/or labile components in carbohydrate matrices is the hygroscopic nature of the matrices produced. Since the glassy matrices are plasticized and solubilized by water as well as softened by heat, it is important that the matrix not come into contact with water, which would permit escape of the volatile component from the matrix. The hygroscopic nature of some prior art matrices requires special precautions to prevent plasticization of the matrix by atmospheric moisture; since, under industrial conditions, it is usually impossible to keep the matrices under completely anhydrous conditions, many prior art compositions require the use of anti-caking agents to prevent caking caused by plasticization of the matrix by moisture adsorbed from the air.
Flavoring compositions comprising a flavoring agent such as a liquid vanilla flavor encapsulated by spray-drying with a maltodextrin carrier are commercially available and are used for introducing the flavoring agent into foodstuffs. In addition to the aforementioned problems, it has been found that these encapsulated products are less effective than is desirable in preventing loss of the volatile flavorant when used in foodstuffs such as cookies, which require addition of the spray-dried compositions to a dough which is subject to extensive manipulation before the production of the final cookie. It appears that the walls of the microcapsules in the spray-dried encapsulated products are so fragile that they rupture easily during manipulation of the dough, and the flavoring agent released by the ruptured microcapsules can then act like an unencapsulated flavoring agent, with resultant loss of flavoring agent, etc.
It has now been found that the problems associated with the use of spray-dried encapsulated flavoring compositions in cookies and other foodstuffs can be eliminated, or at least significantly reduced, by a further encapsulation of the flavoring composition in a glassy matrix which has a high glass transition temperature and which is sufficiently non-hygroscopic that anti-caking agents are not normally required to be used.